ABSTRACT Trypanosoma brucei is a eukaryotic parasite responsible for the disease Human African Trypanosomiasis (HAT), which has an at-risk population of 70 million. HAT is nearly always fatal without treatment, but current medications are expensive, difficult to administer, and rife with adverse side effects. Therefore, there is a need for the development of new drugs. One approach to which is targeting processes that are both essential for parasite survival and pathogen-specific. Ribosome biogenesis is the process of assembling numerous protein and ribosomal RNA components into mature, functional ribosomes. One critical process of ribosome biogenesis is the formation and incorporation of the 5S ribonucleoprotein (RNP) complex into developing 60S ribosomal subunits. Recent high resolution cryo-electron microscopy structures have identified key inter- and intra-subunit interactions between members of the 5S RNP complex and the 60S subunit, which lead to conformational shifts in protein and RNA components of the ribosome. Therefore, the incorporation of the 5S RNP acts as a crucial regulatory checkpoint, with disruption of the process resulting in cessation of ribosome maturation at the level of the 60S subunit. Given that functional ribosomes are required for survival, this makes the assembly and incorporation of the 5S RNP complex a promising target for future drug development. Work in our laboratory has identified the trypanosome-specific proteins P34/P37 as a unique and essential part of the T. brucei 5S RNP. We have also shown direct and unique in vitro interactions between P34/P37 and the protein L5 and 5S rRNA, two well-studied components of the 5S RNP. Recently, we identified T. brucei homologues of the proteins L11, Rpf2 and Rrs1, which are involved in maturation and incorporation of the 5S RNP in yeast. We hypothesize that these homologues form a network of interactions between homologous and unique components of the 5S RNP complex, and are crucial for its formation and incorporation. The specific aims that will be the focus of this project are the following: 1) To characterize the interactions between the T. brucei homologues of L11, Rpf2/Rrs1 and other homologous and unique components of the 5S RNP complex using in vitro studies. 2) Determine the in vivo importance of L11 and Rpf2/Rrs1 in ribosome biogenesis using RNAi knock- down cell lines. HAT remains a significant disease burden on populations in many sub-Saharan African countries, in part due to the many problems associated with current treatments. Using small molecules to target the unique proteins P34/P37 and their essential role as members of the 5S RNP complex is a potential path to developing new treatments to combat HAT. Therefore, characterizing the network of interactions occurring between members of the 5S RNP complex in T. brucei will set a future path toward the development of small molecule chemotherapeutics as novel treatments for HAT.